Some aspects of the radiolysis of poly(methacrylic acid) in oxygen-free aqueous solution

• Published in: Radiation physics and chemistry (Oxford, England : 1993) England : 1993), 1999-10, Vol.56 (4), p.467-474
• Main Authors: Ulanski, P, Bothe, E, von Sonntag, C
• Format: Article
• Language: English
• ISSN: 0969-806X; 1879-0895
• DOI: 10.1016/S0969-806X(99)00332-1

Hydroxyl radicals generated pulse radiolytically in dilute N 2O-saturated aqueous solutions of poly(methacrylic acid) (2.5×10 −3–1×10 −2 mol dm −3, MW=2.8×10 5 Da; p K a≈7) react with this polymer with rate constants of 3.1×10 7 dm 3 mol −1 s −1 (protonated form) and 1.2×10 8 dm 3 mol −1 s −1 (deprotonated form). The primary and secondary carbon-centred radicals thus generated are characterized by an UV spectrum displaying a shoulder at around 320 nm. Changes in the UV spectrum in the 10 ms time range have been attributed to an H-transfer from a methylene group to a primary radical site. The secondary radicals undergo chain scission ( k=1.8 s −1 at pH 7–9) as has been followed by pulse radiolysis with conductometric detection. The ensuing end-chain radicals undergo efficient depolymerization resulting in the release of monomer.